“In this post we describe fan controller which we designed for our 9U wall mount server cabinet. This fan controller is designed to drive a 12V DC cooler fan with pre-configured intervals or by monitoring the temperature of the server cabinet.
Core components of this fan controller is CD4060 binary counter, LM35 temperature sensor and LM358 operational amplifier. In this design CD4060 is used as long duration timer and it can configured to trigger cooler fan from 1-minute and up to 4-hour.
In this design LM35 temperature sensor is used to activate cooler fan in specified temperature. This sensor stage is useful to drive cooler fan when timer stage is in inactive state.
To control the cooler fan we use AP9971 dual N-channel power MOSFET transistor. We design this system to drive 12V cooler fans up to 2A of current. To test this controller we use commonly available 120mm × 120mm, 12V - 300mA brushless DC fan. In our server cabinet we mount this fan to push hot air out of the cabinet.
This fan controller is designed to work with 12V - 1A (or higher) power supply. For the testing and for the final installation, we use 12V - 60W power supply unit which is commonly used for LED lightning projects.”